Traction mechanism



July 6 1926.

O. J. MARTINSON TRACTION MECHANISM Filed March 23, 1926 4 Sheets-Shet 1'July 6 1926.

I 1,591,764 0. J. MARTINSQN TRACTION MECHANISM Filed March 25, 1926 4Sheets-Sheet 2 O. J. MARTlNsON TRACTION MECHANISM July 6,1926. 1,591,764

Filed March 23, 1926 4 sheets-sheet 5 fr-"G. 5

- Lh u I v Jul?" 6 1926.

O. J. MARTENSON TRACTION MECHANI SM Filed March 23, 1926 4 Sheets-Sheet4 Patented July 6, 1926.

UNITED STTS OFFICE.

OSCAR J". MARTINSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO MONIGI'IANMACHINE 00., OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS."

TRACTION MECHANISM.

Application filed March 23, 1926.

This invention relates to walking tractors of the type shown in myco-pending application for patent, filed April 24, 1925, Serial No.25,567, and more particularly to an improved construction of the movableside treads and driving mechanism therefor.

The main objects of the invention are to provide an improved mechanismfor alter nately raising, advancing and lowering the driven machine andits traction means or side treads. Other objects are to provide animproved form eccentric and wrist pin mechanism, whereby the eccentricis allowed to slip at one end of the horizontal movement for raising themachine abruptly to clear the edge of a depression or other obstructionbefore advancing it; to provide a construction of this kind in which theenclosing track structure is effectually and properly guided in theplane of the cam and is properly reinforced and strengthened; and toprovide an improved traction mechanism which is substantial and adaptedto. withstand the severe strains to which such mechanisms are subjectedin the service of large excavating machines and the like.

This invention is chiefly characterized by providing a wrist pin and camslot arrangement of improved design for governing the horizontalmovements of the tread with re spect to the excavator body, togetherwith an eccentric and elongated enclosing track for governing thevertical movements, the slot being provided in a frame structure whichalso serves as a guide for preserving proper alinement of the track andeccentric.

An illustrative embodiment of this invention is shown in theaccompanying drawings, in which:

Figure 1 is a side elevation of the body portion of a drag lineexcavator, showing the improved walking mechanism in operation with theturntable commencing to be tilted to clear obstructions,beforeadvancing.

Fig. 2 shows the same at a time when the tilting is at its maximum andthe turntable is being dragged along the ground.

Fig. 3 shows a position of-the parts when the body has'reached the endof a step and is settling down to a level position.

Fig. 4 is similar to Fig. 1 and shows the side treads in raised positionand advanced half-way in their horizontal movement.

' Fi 5 is a fragmental plan view of one of the s ide treads.

Serial No. 96,822.

Fig. 6 is an end elevation of the excavator with the treads in theposition shown in Fig. 4.

Fig. 6 is an enlarged end elevation and shows the tread lowered.

Fig. 7 is a section on the line 7-7 of Fig. 2.

Fig. 8 is taken on the line 88 of Fig. 2.

Fig. 9 is taken on the line 99 of Fig. 2.

Fig. 10 is a diagram showing the curve representing the path traversedin space by the center of the shaft 7 as the machine moves along.

In the form shown in the drawings, the turntable base 1 normallysupports the body 2. The weight of the body 2 is borne by an annularseries of wheels 8, roughly indicated in Fig. 6, which run on thecircular track 4 of the base 1, and the turntable base 1 is rotatablysecured to a central post (not shown) in the body, so that the base islifted as a unit with the body.

The boom 5, of which a fragment is shown, is attached to one end of thebody 1, and is ordinarily equipped with a drag line bucket or otherexcavating device commonly used. This is usually referred to as thefront of the machine, but since the walking move ments are in adirection away from the boom, the words forward and rearward, as hereinused, should be construed as applying to the direction of travel.

The walking treads 6 are located on each side of the body, and pivotallyattached thereto at a point forward of the center of gravity of thebody, which is weighted, as shown, at one end by the long boom 5. As aresult, when the treads, which work in unison, are thrust downwardly,the advancing edge of the base or turntable 1 is lifted to clear theground, and the rearward portion of the base drags when the excavator ispropelled along on the treads.

For mounting the treads 6, a transverse horizontal shaft 7 is journaledin the body 2 and extends transversely therethrough. The shaft 7 isdriven by an engine which is carried in the body portion 1, but notshown in the drawings.

On the outer ends of the shaft 7 are eecentrically secured a pair offlanged wheels erably positioned at a point diametrically opposite tothe boss in which the squared end of the shaft 7 is secured.

The flanged wheels 8 are embraced by the elongated track frame 9 mountedon the treads 6, and the pins 8.1 fit loosely in vertically disposedguide or cam slots 10 provided in the side guide frames 11 which arerigidly secured across the track frame 9. The track frames 9 are made intwo parts, the upper half 9.1 and the lower half 9.2, which are boltedtogether at the ends. The treads G are pivotally mounted on the loweredges of the track frames, so as to be capable of swinging sidewise tosuit the slope of the ground. Cylindrical parts 12 of the track framesrest on hearing blocks on top of the treads 6, and the latter are heldin place by bearing caps 13, as shown in Figure 9. The side frames 11may be built up, as shown, of two T-shaped sections bolted across thehalves of the track frame 9, the slot 10 being formed between the twosections. In the frame structure just described, the metal is welldistributed for obtaining the maximum longitudinal and transversestrength and stiffness without excess weight. The hori zontal members ofthese side frames 11 prevent the frame 9 from getting out of true foreand aft alinement with the eccentrics 8.

When the weight of the excavator is being borne by the treads and theeccentrics 8 are rolling on the lower straight portion of the track 9,the load is communicated to the treads through the sub-base members 14-.Each member 14 is secured on the top of its tread 6 and has in its upperedge a groove 15 which is concave and concentric with the axis of thecylindrical parts 12. The track frame is provided with a convex circularedge 16 which tits in the groove 15. By this construction the treads maytiltsidewise. The bearing caps 13 are used for lifting the treads.

The track 9 has upper and lower straight portions which both engage thegrooved or flanged eccentric wheel 8, as shown in Fig. 7, and hassemi-circular end portions. The wheel has both rolling and slidingrelation to the track as determined by the action of the wrist pin andslot. The track is then lifted and runs rearwardly with the upperstraight surface bearing on the top of the wheel; and the wheel thenslips in the track as the machine is lifted, the front end of the trackat this time being in contact with the wheel. The slot is suitablycurved to allow for the desired slippage during the lifting of themachine when the cam is at the front end of the track frame.

In Figure 2, the advancing end of the turntable is raised and theexcavator is being dragged forwardly or to the rightof the drawing, thedrive shaft being rotated clockwlse.

In Figure 4, the treads are fully lifted and are being advanced with theupper straight portions of the tracks 9 riding on the tops of the wheels8, which are shown in the highest position with respect to the driveshaft 7.

In Figure 3, the shaft has rotated about degrees from the position shownin Figure 1. The wheel has rolled forwardly in the track and theturntable has about come to rest on the ground. The cam slot being newsubstantially tangent to the motion of the wrist pin, further rotationof the eccentrics will lift the floats or treads rapidly beforeadvancing them.

In Figure 1 the treads are shown fully advanced and the body iscommencing to be lifted. The cam slots are so shaped that the lifting ofthe body or treads is rapid at first with little advancing movement,then the advance is rapid and is accompanied by a gradual lowering ofthe body or treads, as the case may be. The path of the shaft 7 is shownby the curve 17 of Figure 10.

Although but one specific embodiment of this invention has been hereinshown and described, it will be understood that numerous details of theconstruction shown may be altered or omitted without departing from thespirit of this invention, as defined by the following claims.

I claim:

1. In a walking tractor, a body having an eccentric rotatably mountedthereon, said eccentric having a crank pin, and a tread member having ahorizontally elongated opening engaging the eccentric and having a camslot coacting with the crank pin.

2. In a walking tractor, a body, movable treads located on oppositesides of the body, a horizontal shaft rotatably mounted in the body andextending therethrough, flanged wheels eccentrically mounted on the endsof the shaft, upstanding yoke frames attached to each tread and eachhaving an elongated opening in which the respective wheel is engaged, aguide frame secured across each yoke and having a vertically disposedslot, and a crank pin in each eccentric engaging in the responsivevertical slot.

3. In a walking tractor, a body portion, a. horizontal shaft rotatablymounted in the body portion, means for rotating the shaft, a wheeleccentrically mounted on the end of the shaft. a crank pin mounted onthe wheel, and a tread having an upstanding frame having a horizontallyelongated opening for engaging the wheel and having a substan tiallyvertical slot for receiving the crank pin.

4. In a walking tractor, a body portion, a horizontal shaft rotatablymounted in the body portion, means for rotating the shaft, a wheeleccentrically mounted on the end of the shaft, a crank pin mounted onthe wheel,

an endless track frame having a horizontal elongated opening forengaging the periphery of the wheel, a reinforcing frame secured acrossthe track frame at one side thereof, said reinforcing frame having asubstantially vertical slot for receiving the crank pin, and a treadpivotally suspended from the track frame.

5. In combination in a walking tractor a body portion, a driven shaftrotatably mounted in the body portion, a flanged Wheel eccentricallymounted on said shaft, a yoke having an elongated opening in which saidwheel is engaged, said wheel having a crank pin in offset relation withthe shaft, a frame attached across one side of the yoke and having aslot for the crank pin, and a acting with elliptical tracks on thetreads,.

crank pins on said eccentrics, and stationary guld-e means extendingvertically across sald tracks and coacting with said crank pins to.

control the travel of the eccentrics on said tracks.

Signed at Chicago this 9th day of March,

OSCAR J. MARTINSON.

